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Old 28th July 2008, 10:14 PM   #1
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Default Rod Coleman filament supply circuit boards

Hi,
I started planning a board for a filament supply using Rod Coleman's design when I remembered seeing a post of his mentioning doing a run. 'Trouble is, I can't find it today. Does anybody know if it ever happened, or is my memory just a product of wishful thinking?

Also: Have any others built this supply circuit? Any comments or tips from your own experience?


Thanks very much
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Old 28th July 2008, 11:28 PM   #2
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I think the thing to do is ask Rod himself.
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Old 29th July 2008, 12:56 AM   #3
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Hi Andy,
I'd love to contact him but I'm just joined and my account is under moderation for a while.
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Old 29th July 2008, 08:29 AM   #4
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I've emailed Rod, so will inform. I'm an interested party since I only use DHTs.


andy
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Old 30th July 2008, 12:34 PM   #5
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It's true I was planning on a PCB for the DHT heater. As usual with these things, there are insufficient hours in a day, and it didn't get beyond a notion.

Other more industrious friends on the forum have already created & proved a design, and we are looking at possible ways to make it available. (thanks to Pete)

One possibility is to make the design files available (Eagle based) so that DIYers can forward them to Olimex

http://www.olimex.com/pcb/index.html

who do a good job, including panelisation for a nice price. Panelisation is ideal for this design, since their DSS is only 30 Euros, and you get a good number of DHT heat boards out of that (100x160mm).

It hardly seems worth organising a group buy, when these piece prices are so low.
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Old 30th July 2008, 02:42 PM   #6
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I was waiting for an OK from Rod on this. Piotr and myself did a shootout of filament design possibilities and have made a small run of experimental boards with Rod's consent - they worked just fine and sounded good. Rod's is the best design I've heard out of those I've tried (excludes choke input).

The board we commissioned was in fact quite tiny - half a credit card size. It should be possible, depending from an OK from Piotr who is on holiday, to scare up some more boards from the same source, which Is in Bulgaria if my memory is right. So I would have thought we could get some boards to DIY-ers one way or another.

Andy
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Old 30th July 2008, 09:04 PM   #7
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Sorry Andy! didn't appreciate you were waiting for me.

By all means go ahead and circulate the design through the forum. For DIY noncommercial use of course!

Perhaps if the PCB were a little bigger, we could include some high-power heatsink-mounted resistors for BIG DHT filament heat?

Rod
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Old 31st July 2008, 11:27 AM   #8
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Thanks very much to both of you !

Quote:
From Andy - ". . . . . the best design I've heard out of those I've tried (excludes choke input)."
Andy, Did you mean by that that you liked choke input or that you hadn't tried it in the shootout?
I've tried a few LCLC supplies that worked well and what really caught my attention over Rod's design was that I was in the process of wiring up a (described in series) L(cmc) >C> L> Fil> L > Neg. term of C > back out through other leg of CMC. This has a 431 controlled power transistor as a shunt reg. across the fil. It's not finished yet as other stuff is demanding my time but I hope to have it running in the next couple of weeks. (Trying batteries now)

Quote:
. . . .So I would have thought we could get some boards to DIY-ers one way or another.
I'd certainly be into that if you do!


Quote:
From Rod - "Perhaps if the PCB were a little bigger, we could include some high-power heatsink-mounted resistors for BIG DHT filament heat?"

I'd very much like to try your design on both low and high power filaments . (When I posted I had been doodling a block layout with transistors and power resistors on the long edge of a narrow strip so that they could be bolted through heat sink pads to the metal side of a chassis and caps in a row down the other side. . . .'don't know yet whether the traces will work out well that way or not.)

Anyway, thanks very much !!
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Old 31st July 2008, 12:46 PM   #9
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Quote:
Originally posted by Rod Coleman
Sorry Andy! didn't appreciate you were waiting for me.

By all means go ahead and circulate the design through the forum. For DIY noncommercial use of course!

Perhaps if the PCB were a little bigger, we could include some high-power heatsink-mounted resistors for BIG DHT filament heat?

Rod
Yes, please publish the design.

TIA,

-- josť k.
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Old 31st July 2008, 01:26 PM   #10
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To answer a few of these questions. I built and listened to a few different filament supplies. I didn't build a choke input one, and haven't heard that as a comparison - I'm sure it's excellent but I need something smaller. As a result of listening tests I and Piotr would rank them as follows:

Rod's design
Current source using LM1084
Voltage regs using LM1084 plus CMC at the end
Voltage regs using LM1084 (no CMC)
Current source using LM1084 plus CMC at the end (didn't sound good)

I built all these on strips of tag board to test out. Piotr and I then discussed doing a prototype PCB with Rod, who was agreeable and most helpful (excellent guy).

Piotr then designed the layout and we commissioned the PCBs from an E.European source that Piotr uses. We used the PCBs successfully in a few projects and they seemed reliable if used within spec. At this stage we've run out of boards, but we could get some more done. They are quite tiny - half a credit card size.

Piotr is away currently so he should be included in all this.

The design of the filament supply is in this forum in this thread

New DHT heater

Andy
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